Abstract-Femtocell has been considered by the wireless industry as a promising solution not only to improve indoor coverage, but also to unload traffic from overburdened macrocell networks. In hybrid macro/femto networks, macrocells may have to share the same spectrum with femtocells, due to spectrum availability and network infrastructure considerations, in spite of potentially excessive interference caused by densely deployed femtocells. In this paper, we propose a decentralized resource allocation scheme for the orthogonal frequency division multiple access (OFDMA) downlink of a shared-spectrum macro/femto network, where each femtocell randomly selects a subset of available OFDMA resources for transmission, in order to achieve decentralized inter-cell interference avoidance. The performance of the decentralized resource allocation scheme is evaluated by simulations based on per-cell or network-wide performance metrics. Simulation results provide insights on how the resource allocation in a shared-spectrum hybrid macro/femto network should take into account the spatial density of femtocells and indoor/outdoor radio propagation channel conditions. Keywords-Femtocell, macrocell, OFDMA, resource block (RB), outage probability, areal spectral efficiency (ASE).

Abstract-In this correspondence, a two-channel linear phase finite-impulse-response (FIR) quadrature mirror filter (QMF) bank minimax design problem is formulated as a nonconvex optimization problem so that a weighted sum of the maximum amplitude distortion of the filter bank, the maximum passband ripple magnitude and the maximum stopband ripple magnitude of the prototype filter is minimized subject to specifications on these performances. A modified filled function method is proposed for finding the global minimum of the nonconvex optimization problem. Computer numerical simulations show that our proposed design method is efficient and effective.

For an orthogonal frequency division multiple access (OFDMA) downlink of a spectrally coexisting macro and femto network, a resource allocation scheme would aim to maximize the area spectral efficiency (ASE) subject to constraints on the radio resources per transmission interval accessible by each femtocell. An optimal resource allocation scheme for completely decentralized deployments leads however to a nonconvex optimization problem. In this paper, a filled function method is employed to find the global maximum of the optimization problem. Simulation results show that our proposed method is efficient and effective.

This paper proposes an optimal cosine modulated nonuniform linear phase finite impulse response (FIR) filter bank design. The frequency responses of all the analysis filters and the synthesis filters of the filter bank are derived based on both stretching and shifting the frequency response of the prototype filter. The total aliasing error of the filter bank is minimized subject to a specification on the maximum amplitude distortion of the filter bank as well as specifications on both the maximum passband ripple magnitude and the maximum stopband ripple magnitude of the prototype filter. This filter bank design problem is actually a functional inequality constrained optimization problem. Our recently developed integration approach is employed for solving the problem. Computer numerical simulation results show that our proposed design method outperforms existing design methods.I.

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